WESTERLY — All customers of the municipal water system are being asked to boil their water before using it. The boil water advisory was issued this evening after a routine sample collected Monday and tested Tuesday came back positive for E. coli, an indicator harmful bacteria could be present in the water.

The fecal indicator was found in a sample taken from a water system well in Bradford. The well has since been isolated from the system. Follow up samples taken from throughout the distribution system did not detect the presence of actual bacteria. Paul Corina, public works director, said the Water Department followed the steps outlined by the state Department of Health for when samples test positive. The initial positive result was reported to local officials late Tuesday afternoon.

Pawcatuck residents who don’t have wells are served by the Westerly municipal system.

Customers of the water system are being asked not to drink the water without boiling it first. According to an advisory issued by the water department, water should be allowed to boil for at least one minute and allowed to cool before drinking. Boiled or bottled water should also be used for making ice, brushing teeth, washing dishes, and food preparation until further notice. Boiling kills bacteria and organisms in the water.

Fecal indicators are microbes whose presence indicates that the water may be contaminated with human or animal wastes. Microbes in these wastes can cause short-term health effects such as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health risk for infants, young children, some of the elderly, and people with severely compromised immune systems. The symptoms can also be caused by other conditions. Those who experience prolonged symptoms should consider seeking medical advice, according to the advisory. Those at increased risk are asked to seek advice from their health care providers.

Additional samples from throughout the distribution system will be taken Thursday. Local officials expect to receive those results on Friday.

The Water Department will announce when tests show no E. coli and the boil water advisory is lifted. For more information, call Paul Corina, director of public works, at 401-348-2561. General guidelines on ways to lessen the risk of infection by microbes are available from the federal Environmental Protection Agency’s safe drinking water hotline at 1-800-426-4791.

Customers are asked to share this information with all people who drink water from the municipal system, especially those who may not have received a notice directly.